Various forms of multi-unit does inhalers are known and among these are ones in which a main housing contains a blister pack. The blister pack has a plurality of blisters each defining a container having a dosage of medicament and which are burst individually in order for a user to inhale the medicament. The blisters remain joined to a carrier during extraction of the medicament.
Further multi-unit does inhalers include those using capsules which are held in a rotating magazine. One end of a capsule is pulled away from the other to allow access of air to the contents, whereby they can be inhaled. Alternatively the capsules may be pierced to gain access to their contents after which the user may inhale the medicament.
In such an arrangement the extraction of medicament usually occurs as a result of an inhaled airstream passing over a capsule or other container.
It is necessary to provide access to the contents of a capsule or blister pack. This can be done by piercing the container, which may lead to the drawback of needing to provide piercing pins in the inhaler and which, if an inhaler is handled carelessly, could cause discomfort. Also, if a container is pierced in situ it can lead to fragments of the container being inhaled with the contents.
It is a disadvantage of most known inhalers that not all of the medicament, or even a large proportion of it, is drawn from the capsule, or the separated capsule cap and body portions, or the blister pack.
It is known that a swirling chamber using a combination of pneumatic action, centrifugal action, and impact to extract medicament from a capsule is very effective and it is preferred that the inhaler should be capable of using such actions in such a swirling chamber without over-complicating the device.
Preferably a capsule should be automatically loaded and pierced without loss of contents prior to entry into the medicament chamber.
However, the spent capsules must then be removed in order to allow access for the next unused capsule.
It is a disadvantage of known inhalers that it is often necessary to carry out many manipulative movements and capsule transfers before the medicament can be inhaled. In the case of someone who is unable, especially at the time the medicament is most needed, to perform all these functions these known inhalers can be inconvenient.
Further, it is not often, if ever, clear how many capsules a magazine has still left. Even if it can be seen how many are left, if all the capsules have been used it will still be possible for the user to attempt to inhale (on a used capsule).